Start free

Physics · Wave Optics

NEET (UG) 2025 — Question 40

The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5∘22.5^{\circ} from the polarization axis of one of the polaroid, is ( I0\mathrm{I}_{0} is the intensity of polarised light after passing through the first polaroid):

  1. Option A:

    I02\frac{\mathrm{I}_{0}}{2}

  2. Option B:

    I04\frac{I_{0}}{4}

  3. Option C:

    I08\frac{\mathrm{I}_{0}}{8}

    Correct
  4. Option D:

    I016\frac{\mathrm{I}_{0}}{16}

Answer: C

Step-by-step solution

Initially two polaroids are crossed i.e. 90∘90^{\circ}

figure

After passing from first polaroid intensity is I0\mathrm{I}_{0}

Iunpolarised →AI0→CI0cos⁡2θ→BI0cos⁡2θcos⁡2θ(90−θ)⇒I04sin⁡2(2θ)⇒I04sin⁡2(2×22.5)⇒I08\begin{aligned} & I_{\text {unpolarised }} \xrightarrow{A} I_{0} \xrightarrow{C} I_{0} \cos ^{2} \theta \xrightarrow{B} \\& I_{0} \cos ^{2} \theta \cos ^{2} \theta(90-\theta) \\& \Rightarrow \frac{I_{0}}{4} \sin ^{2}(2 \theta) \\& \Rightarrow \frac{I_{0}}{4} \sin ^{2}(2 \times 22.5) \\& \Rightarrow \frac{I_{0}}{8} \end{aligned}

Answer key and solution verified before publishing.

Practise Wave Optics

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Solve a similar one free
Exam
NEET (UG) 2025
Paper
2025 paper
Subject
Physics
Chapter
Wave Optics
Topic
Polarization of Light Waves

More Wave Optics questions from this paper